Sorafix Dyes

Sorafix dyes are a special reactive colorant that can be used to color leather. These special reactive dyes have a unique feature the versatility of the application procedures allowing dyes to be applied at temperatures ranging from 110 -145 Fahrenheit. These dyes do not have built in insolubility or a level of substantivity. Therefore, small dyes possessing rapid diffusion properties can be made. This allows leveling and dyeing very rapidly when compared to other dyes. 

Leather is a natural, breathable material that is very hard-wearing, but it is being replaced with textile fabrics and plastic, as these materials have better wash, perspiration, rub and migration fastness properties. Regular leather dyes, which are mostly composed of anionic acids, direct dyes, and sulfur dyes that are fixed through ionic interactions to collagen. With high positive charge of the leather, the interaction of these anionic dyes becomes stronger. This explains, why chrome tanned leather being more cationic, usually exhibits much better wet fastness than chrome free leather which is more anionic. At the same time, the problem is that these ionic interactions are not strong enough to resist the conditions that leather is exposed during its life like soap and perspiration solutions. The result is that the ionic interactions are loosened and therefore some of the dye is released from the collagen fibers under these conditions, coloring solutions and staining materials such as plastics, textiles, or skin on contact.  

This issue can be solved by using our Sorafix dyes. These dyes form strong chemicals bonds with the collagen fibers instead of ionic interactions. These chemicals bonds remain stable, regardless of any changes in the charge of the substrate that is to be dyed, with the result that the same superior wet fastness can be obtained on both wet blue and wet white leather. The chemical bond is stable under the conditions of use and the leather does not stain other materials that could be in contact with.  

The process to dye the leather with Sorafix dyes differs from conventional dyeing processes. The process that is used to fix these dyes on leather has careful control of the process parameters so that all the dye can be fixed to the collagen fibers. First the neutralization step is achieved then the dye is added. The PH must be between 7.2-7.9 for the dye to penetrate the leather through cross section then PH must be raised to between 9.2-10.1 using an alkaline chemical product and the dye is fixed to the leather. If the process is performed properly, the dye is distributed evenly across the surface of leather and through the cross section with almost all of dye applied is bonded to the collagen fiber that makes possible to have an excellent wet fastness.  

A small amount of dye reacts with water resulting with fibers that are no longer bonded to the collagen fiber. It is recommended that the float then be drained, and leather must be wash until float is clear after that formic acid can be added in a fresh float and the leather can be re-tanned and fat liquored. Sorafix dyes can be used for different types of leather including Nappa leather, floater leather, suede leather, glove leather, etc. If you are interested in learning more or contacting us, click the picture below! 

By |February 5th, 2021|Blog|0 Comments

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Jesus Medina is Technical Manager Americas for First Source Worldwide with vast experience in colorants and the leather industry. His persistence helps him excel at solving customer problems and identifying application opportunities. You can usually find him in the lab, enthusiastically whistling while he works.